Neonatal intensive care has been studied from an epidemiological, ethical, medical and even sociological perspective, but little is known about the impact of parental involvement in decision-making, especially in critical cases. We rely here on a comparative, case-based approach to study the parental role in decision-making within two technologically identical but culturally and institutionally different contexts: France and the United States. These contexts rely on two opposed models of decision-making: parental autonomy in the United States and medical paternalism in France. This paternalism model excludes parents from the decision-making process. We investigate whether parental involvement leads to different outcomes from exclusively medically determined decisions or whether "technological imperatives" outplay all other factors to shape a unique, 'medically optimal' outcome. Using empirical data generated from extensive ethnographic fieldwork, in-depth interviews with 60 clinicians and 71 parents and chart review over a year in two neonatal intensive care units (one in France and one in the US), we analyze the factors that can explain the observed differences in decision-making in medically identical cases. Parental involvement and the legal context play a less role than physicians' differential use of certainty versus uncertainty in prognosis, a conclusion that corroborates the fact that medical control over ethical dilemmas remains even in the context of autonomy. French physicians do not ask parents permission to withdraw care (as expected in a paternalistic context); but symmetrically, American neonatologists (despite the prevailing autonomy model) tend not to ask permission to continue. The study provides an analysis of the making of "ethics", with an emphasis on how decisions are conceptualized as ethical dilemmas. The final conclusion is that the ongoing medical authority on ethics remains the key issue.